An Overlay Transport Virtualization (OTV) protocol has been developed to connect a layer 2 network domain that spans across multiple data center sites. The OTV protocol uses a “MAC-in-Internet Protocol (IP)” encapsulation technique to extend the layer 2 domain logically over a layer 3 IP network. Since the OTV protocol uses IP, it does not require any pseudo-wire or tunnel maintenance and provides multi-point connectivity using any available transport.
To avoid issues with data loops and the Spanning Tree Protocol (STP), the OTV protocol supports only a per-virtual local area network (VLAN) load-balancing. For a given VLAN, only one OTV edge switch is permitted to forward packets in and out of the network. This edge switch is known as an authorized edge device (AED).